1. Field of Invention
This invention relates to etching processes. More specifically, this invention relates to processes for wet chemical etching ion-implanted III-V nitride and III-V nitride alloy films.
2. Description of Related Art
Blue light emitting diodes and blue laser diodes are important for many uses, including printing, data storage, medical technology and displays. Gallium nitride ("GaN") and aluminum gallium indium nitride ("AlGaInN") alloys are being developed for visible and UV light emitters, and for high temperature electronic devices. High quality GaN films have been obtained by epitaxial deposition on sapphire substrates, leading to efficient blue and green light emitting diodes. Such GaN films are currently being incorporated into heterojunction laser diodes.
For the development and fabrication of devices emitting blue or green light, a high quality technique for controllably removing III-V nitride material after growth is essential. For example, to fabricate laser diodes from III-V nitride semiconductors, the formation of either mesa structures from multilayer nitride films, as shown in FIG. 2D, or facets will be necessary.
To date, primarily dry chemical etching techniques have been employed to etch III-V nitride materials. For example, processes involving reactive ion etching ("RIE") with plasmas of various chlorine containing gases have been demonstrated. More effectively, nitrides are etched by chemically assisted ion beam etching ("CAIBE"), using an Ar ion beam in combination with proximity injection of a chlorine-containing gas. However, these techniques require a substantial investment in equipment and technique and are usually not justifiable in the early research stage of the development of III-V nitride based devices.
It has been found that GaN is chemically resistant to most of the acids and bases that are commonly used in the semiconductor technology. For example, GaN is not affected when exposed to boiling aqua regia or HF. Similarly, GaN material of low crystalline quality having donors in excess of 10.sup.19 cm.sup.-3 is etched only very slowly by hot sodium hydroxide (NaOH) or potassium hydroxide (KOH).
There is a need for a process for chemically etching III-V nitride and III-V nitride alloy materials.